US nuclear officials have claimed that the Fukushima plant is spilling far higher radiation levels than first thought. U.S. individuals on the ground are analysing the data separately from those working for the Japanese government.

President Barack Obama’s spokesman Jay Carney said: “We are concerned enough that we have offered a great deal of assistance to the Japanese and we have our own experts on the ground both assisting and evaluating information independently.”

The UK foreign office released this warning on Wednesday for UK citizens currently in Japan, even those outside of the current 20km exclusion zone around Fukushima:

“Due to the evolving situation at the Fukushima nuclear facility and potential disruptions to the supply of goods, transport, communications, power and other infrastructure, British nationals currently in Tokyo and to the north of Tokyo should consider leaving the area.”

Gregory Jazcko of the U.S. Nuclear Regulatory Commission said that it was their belief that there is no water covering the burnt fuel rods in unit 4 of the Fukushima plant.

He said on Wednesday: “There is no water in the spent fuel pool and we believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures.”

“If they don’t get water to these spent fuel pools in view of the containment breaches in the other plants the actual radiation releases could approach that category of Chernobyl.”

Hard to get ones mind round the threat as now described by the US regulatory authorities. Yet from what we do know here the US analysis does sound right.Jon Snow, from Tokyo late on Wednesday evening

The IAEA reportedly said that the temperature of the fuel pool in unit 4 was as high as 84 degrees celsius, well above the recommended temperature of below 25 degrees celsius.

The advise from the U.S. is for their citizens to impose a more cautious 50km exclusion zone around the stricken nuclear plant.

This was in stark contrast to statements from the Japan Nuclear Agency who insist that the levels of radiation have fallen throughout Wednesday. Japan’s Nuclear and Industrial Safety Agency said that in the last 24 hours the amount of recorded radiation had more than halved.

White smoke or steam billowed from the Fukushima plant on Wednesday after a series of explosions and fires damaged reactors and caused radiation leaks.

French Industry Minister Eric Besson said: “Let’s not beat about the bush. They have visibly lost the essential of control [of the situation]. That is our analysis, in any case, it’s not what they are saying,” Mr Besson told BFM television.

Let’s not beat around the bush. They have visibly lost the essential of control. French Industry Minister Eric Besson

A helicopter attempting to pour water into the reactors turned back due to radiation, and workers battling the rising temperatures were temporarily evacuated due to high radiation levels, which peaked at 1,000 millisieverts – a level very harmful to human health – before falling again.

The police have even been drafted in to help, turning to water cannons to try and get water into the reactors.

The International Atomic Energy Authority said the Japanese authorities had reported “concerns” about the condition of the spent nuclear fuel pool at Reactors No 3 and 4.

The 180 workers are now back at the plant and owner Tepco said they were also trying to cool two other reactors – 5 and 6 – after the problems with the initial four.

Walt Patterson, an authority on nuclear power and associate fellow at thinktank Chatham House, told Channel 4 News: “What is happening at the reactor site now is probably pretty serious panic as the circumstances in which they are trying to control these reactors gets more and more difficult.

“Also whether they have reliable information from the control room and their dials and gauges – I’m beginning to guess they probably don’t – means they may have no idea what the condition of the reactor is,” he added.

Mr Patterson said in such a high pressured situation a catastrophic mistake could be made: “It’s probably terrifying there right now, they could easily make a mistake. At Three Mile Island, one operator did something which he thought was the right thing but was actually the wrong thing and it nearly triggered a complete meltdown.”

Evacuations

Hundreds of thousands of people have been evacuated and those remaining within a 30km radius of the plant were urged to stay indoors over fears of a potential full-scale meltdown. The Japanese Government asked for help from private companies to help deliver supplies.

In a rare appearance, the Japanese Emperor Akihito said he was “deeply worried” by the situation at the nuclear plant and “deeply hurt by the situation” across Japan caused by the tsunami and earthquake.

“People would not be in immediate danger if they went outside with these levels. I want people to understand this,” said Yukio Edano, referring to people living outside the 30km exclusion zone.

However the advice to foreigners living in Japan has been contradictory, with french citizens in Tokyo advised by their government to leave the country or head to southern Japan, while the US authorities have advised their citizens to move at least eighty kilometres away from the stricken Fukushima plant – a much wider area than the Japanese government’s evacuation zone – or stay indoors.

The British Foreign Office has advised against non-essential travel to Tokyo and on Wednesday advised that in the light of “the evolving situation at the Fukushima nuclear facility and potential disruptions to the supply of goods, transport, communications, power and other infrastructure, British nationals currently in Tokyo and to the north of Tokyo should consider leaving the area.”

Five days in JapanThere is a strange abandon in a reporter confronted with unimaginable human loss and unbelievable invisible threat, writes Channel 4 News Presenter Jon Snow in Japan.

The radiation cloud. The unseen nuclear threat – I can see so much, that I have no brain space left to imagine what I cannot see. And you imagine what is happening to the 50 men and women still inside the Fukushima power station battling to keep the coolant flowing to prevent total meltdown.

Five days in Japan. Five days that have crashed an economy. Five days that have etched epitaphs on tombstones that will never host the victims they record; epitaphs that will include as victims, Japan's generating capacity and possibly the very future of nuclear power generation itself. Five days in Japan that define the Japanese identity – resilient, lacking self pity, restrained with its grief, uncomplaining. Five days that define Japanese efficiency, manpower, skill, team work.

At one point, radiation levels in Tokyo – more than 150 miles away – reached ten times normal levels, but were not a threat to human health, officials said. Winds over the plant were forecast to blow from the northwest during Wednesday, which would take radiation towards the Pacific Ocean.

Nuclear experts said the attempts were last-ditch efforts to tackle the disaster, which is set to be remembered as one of the world’s worst industrial crises.

“We do not have all the details of the information so what we can do is limited. I am trying to improve the communication,” Yukiya Amano said.

Reactors

Tepco is taking action to cool all six reactors at the Fukushima plant. The key problems now, the operator said,are with reactors No 3 and 4.

Reactor 3 was damaged in an explosion earlier this week, and 4 – a non-operational reactor which houses a pool of spent nuclear fuel – has been damaged in two fires and the nearby explosion.

“The situation at the No 4 reactor is not exactly a good situation but the No 3 reactor is a higher priority,” a Tokyo Electric Power official told a media briefing.

He said they were unsure why pressure had suddenly dropped in the No 2 reactor. The company said this might indicate it was being cooled or it could also be an ominous sign that there was a hole in the core container, or it might just be a faulty pressure reading.

“We cannot with certainty say whether or not the core container is airtight,” the company official said.

The company also said it was pouring water at the reactors No.5 and No. 6, where temperatures had risen slightly.

Crippled

Japan remains crippled by a triple hit of disasters – the 8.9 magnitude earthquake and tsunami on Friday, and the ongoing nuclear scare.

'People need to be told'"In a crisis, you have to be timely, open and frank," risk management expert Mike Granatt told Channel 4 News. "You have to answer questions and regularly, and bring certainty even where there is none - say what you know, say what you don't.

"There has to be a regular flow of information from people they trust - one of the problems in Japan is that people do not trust the company. That's a very big handicap and the only way round it is to get someone in, someone independent, who is trusted.

"And you have got to give decent advice. You also need to give scale, what sort of doses the radiation compares to, a CAT scan, for example. If something like this happened in the British context, I would be looking at two hour press conferences, and information published on the website the whole time, including a map of where the radiation is.

"It's important to tell people when they are in danger - but also when they are not. I think in Japan they know what they are supposed to do but they are in the worst of all situations, they've had so many disasters, and now they do not know what is going on inside the reactor - what they have to do is make an intelligent guess and follow the procedures.

"There are four things that characterise a crisis - first the certainty starts to go, then you start to lose control, then the third thing is you can become isolated as an organisation, people don't believe you, then last you end up being attacked. If they want to regain control of this crisis, they have to assert pretty firm control both in terms of managing the situation and people's expectations."

Mike Granatt is a risk management expert and former founding head of the Cabinet Office Civil Contingencies Secretariat.

Panic over the situation wiped $620bn off Japan’s stock market over Monday and Tuesday, but it has since rebounded slightly. Estimates suggest the disasters have caused Japan losses of up to $200bn in total in output.

Many flights to Japan have been cancelled and France urged its citizens to leave or head south.

Meanwhile recovery workers are trying to clean up the tsunami damage and get Japan back on track – a huge feat when whole towns were simply wiped out by the colossal wave. Serious aftershocks also continue to hit the country.

Bitingly cold weather and snow in some areas added to the misery of those who have lost their homes and livelihoods, as well as possibly family members.

The death toll stands at around 4,000, but is expected to rise. Tens of thousands remain missing.